Solving computer Wi-Fi problems?

Okay, since late last night I've been unable to connect to my home internet using my laptop's internal Wi-Fi adapter. I memorised the passcode so I know it's right, but when I input the code to try and connect it says "the network key is incorrect. Please try again." I know that it's right because it was working yesterday. I have the free few however many days (summet like 60 days) of Norton Internet Security that came with my laptop running and have done since I got the laptop. I've downloaded multiple mods for minecraft, I downloaded two or three last night also. Next to that I found that there was a flash virus trying to get through, norton told me, and kept closing webpages I was trying to look at. So I uninstalled flash and reinstalled it but when I went to youtube I couldn't watch any videos because of flash. So I restarted my laptop to try and get it to work and on restart the internet wasn't working (the aformentioned problem) so I did multiple restarts to try and fix it to no avail. So i did a system restore to the last restore point that worked. But still no internet. I've plugged in the stupid Wi-Fi adaptor to use the internet for now, and youtube works and everything works fine except the internet. Someone help